128 lines
3.7 KiB
Plaintext
128 lines
3.7 KiB
Plaintext
<!--
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doc/src/sgml/ref/pgtestfsync.sgml
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PostgreSQL documentation
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-->
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<refentry id="pgtestfsync">
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<indexterm zone="pgtestfsync">
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<primary>pg_test_fsync</primary>
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</indexterm>
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<refmeta>
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<refentrytitle><application>pg_test_fsync</application></refentrytitle>
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<manvolnum>1</manvolnum>
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<refmiscinfo>Application</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>pg_test_fsync</refname>
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<refpurpose>determine fastest <varname>wal_sync_method</varname> for <productname>PostgreSQL</productname></refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<cmdsynopsis>
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<command>pg_test_fsync</command>
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<arg rep="repeat"><replaceable>option</replaceable></arg>
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</cmdsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>
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<application>pg_test_fsync</application> is intended to give you a reasonable
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idea of what the fastest <xref linkend="guc-wal-sync-method"/> is on your
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specific system,
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as well as supplying diagnostic information in the event of an identified I/O
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problem. However, differences shown by
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<application>pg_test_fsync</application> might not make any significant
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difference in real database throughput, especially since many database servers
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are not speed-limited by their write-ahead logs.
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<application>pg_test_fsync</application> reports average file sync operation
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time in microseconds for each <literal>wal_sync_method</literal>, which can also be used to
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inform efforts to optimize the value of <xref linkend="guc-commit-delay"/>.
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</para>
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</refsect1>
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<refsect1>
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<title>Options</title>
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<para>
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<application>pg_test_fsync</application> accepts the following
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command-line options:
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<variablelist>
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<varlistentry>
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<term><option>-f</option></term>
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<term><option>--filename</option></term>
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<listitem>
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<para>
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Specifies the file name to write test data in.
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This file should be in the same file system that the
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<filename>pg_wal</filename> directory is or will be placed in.
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(<filename>pg_wal</filename> contains the <acronym>WAL</acronym> files.)
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The default is <filename>pg_test_fsync.out</filename> in the current
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directory.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-s</option></term>
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<term><option>--secs-per-test</option></term>
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<listitem>
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<para>
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Specifies the number of seconds for each test. The more time
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per test, the greater the test's accuracy, but the longer it takes
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to run. The default is 5 seconds, which allows the program to
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complete in under 2 minutes.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-V</option></term>
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<term><option>--version</option></term>
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<listitem>
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<para>
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Print the <application>pg_test_fsync</application> version and exit.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-?</option></term>
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<term><option>--help</option></term>
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<listitem>
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<para>
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Show help about <application>pg_test_fsync</application> command line
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arguments, and exit.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect1>
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<refsect1>
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<title>Environment</title>
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<para>
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The environment variable <envar>PG_COLOR</envar> specifies whether to use
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color in diagnostic messages. Possible values are
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<literal>always</literal>, <literal>auto</literal> and
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<literal>never</literal>.
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</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<simplelist type="inline">
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<member><xref linkend="app-postgres"/></member>
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</simplelist>
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</refsect1>
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</refentry>
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